Automated test equipment (ATE) can be any testing assembly that performs a test on a device, semiconductor wafer or die, etc. ATE assemblies may be used to execute automated tests that quickly perform measurements and generate test results that can then be analyzed. An ATE assembly may be anything from a computer system coupled to a meter, to a complicated automated test assembly that may include a custom, dedicated computer control system and many different test instruments that are capable of automatically testing electronics parts and/or semiconductor. Automatic Test Equipment (ATE) is commonly used within the field of electrical chip manufacturing. ATE systems both reduce the amount of time spent on testing devices to ensure that the device functions as designed and serve as a diagnostic tool to determine the presence of faulty components within a given device before it reaches the consumer.
In testing devices or products, e.g. after production, it is crucial to achieve among other factors a high product quality, an estimation of the device or product performance, a feedback concerning the manufacturing process and finally a high customer contentment. Usually a plurality of tests is performed in order to ensure the correct function of a device or product, commonly referred to as a device under test (“DUT”) in testing parlance. The plurality of tests is typically part of a test plan that is loaded into the ATE system by the user. The test plan acts as a blueprint for running the tests on the DUTs. The plurality of tests may be compiled in a test flow wherein the test flow may be separated into different test groups which contain one or more tests for testing the device or product. For example, a semiconductor device may be tested with a test flow comprising contact tests, current-voltage tests, logic tests, speed tests, stress tests and functional tests.
One typical problem that commonly arises in ATE systems, especially ones that perform low current measurements, e.g., pico-amps, is the presence of thermal electromotive force (EMF). The presence of thermal EMF can adversely affect low resistance measurement accuracy. Every connection made with dissimilar metals creates an unwanted thermocouple in the measurement circuit. Each of these unwanted thermocouples generates an error voltage that varies with temperature gradients in the system. These can be on the order of many microvolts that can cause significant errors in low-ohm measurements. Accordingly, when performing low current measurements, thermal EMF can be a significant source of error and the user needs to be able to characterize this type of error to be able to effectively account for it when performing measurements. Calibration processes in conventional ATE systems do not have the capability of taking into account the differences in thermal EMF in all the different pairs of signal paths. As a result, thermal EMF is a significant limitation in improving measurement accuracy in conventional ATE systems.